Random screening of molecules for possible activity as therapeutic agents has occurred for many years and resulted in a number of important drug discoveries. While advances in molecular biology and computational chemistry have led to increased interest in what has been termed “rational drug design,” such techniques have not proven as fast or reliable as initially predicted. Thus, in recent years there has been a renewed interest and return to random drug screening. To this end, particular strides having been made in new technologies based on the development of combinatorial chemistry libraries, and the screening of such libraries in search for biologically active members.
Initially, combinatorial chemistry libraries were generally limited to members of peptide or nucleotide origin.
While combinatorial libraries containing members of peptide and nucleotide origin are of significant value, there is still a need in the art for libraries containing members of different origin. For example, traditional peptide libraries to a large extent merely vary the amino acid sequence to generate library members. While it is well recognized that the secondary structures of peptides are important to biological activity, such peptide libraries do not impart a constrained secondary structure to its library members.
To this end, some researchers have cyclized peptides with disulfide bridges in an attempt to provide a more constrained secondary structure (Tumelty et al., J. Chem. Soc. 1067-68, 1994; Eichler et al., Peptide Res. 7:300-306, 1994). However, such cyclized peptides are generally still quite flexible and are poorly bioavailable, and thus have met with only limited success.
More recently, non-peptide compounds have been developed which more closely mimic the secondary structure of reverse-turns found in biologically active proteins or peptides. For example, U.S. Pat. No. 5,440,013 to Kahn and published PCT Applications Nos. WO94/03494, WO01/00210A1, and WO01/16135A2 to Kahn each disclose conformationally constrained, non-peptidic compounds, which mimic the three-dimensional structure of reverse-turns. In addition, U.S. Pat. No. 5,929,237 and its continuation-in-part U.S. Pat. No. 6,013,458, both to Kahn, disclose conformationally constrained compounds which mimic the secondary structure of reverse-turn regions of biologically active peptides and proteins. The synthesis and identification of conformationally constrained, reverse-turn mimetics and their application to diseases were well reviewed by Obrecht (Advances in Med. Chem., 4, 1-68, 1999).
While significant advances have been made in the synthesis and identification of conformationally constrained, reverse-turn mimetics, there remains a need in the art for small molecules which mimic the secondary structure of peptides. There is also a need in the art for libraries containing such members, as well as techniques for synthesizing and screening the library members against targets of interest, particularly biological targets, to identify bioactive library members.
In the mean time, a proto-oncogene is a normal gene that can become an oncogene due to mutations or increased expression. c-Myc (MYC) is known as one of the proto-oncogenes, and dysregulation of c-Myc is considered one of a series of oncogenic events required for mammalian tumorigenesis (Pelengaris S, Khan M. The many faces of c-MYC. Arch Biochem Biophys. 2003; 416:129-136). MYC dysregulation, via a variety of mechanisms, was also found to be associated with myeloid leukemias (Hoffman B, Amanullah A, Shafarenko M, Liebermann D A. The proto-oncogene c-myc in hematopoietic development and leukemogenesis. Oncogene. 2002; 21: 3414-3421). In addition, c-Myc was found to rapidly induce acute myeloid leukemia (Hui Luo et al. “c-Myc rapidly induces acute myeloid leukemia in mice without evidence of lymphoma-associated antiapoptotic mutations,” Blood, 1 Oct. 2005, volume 106, Number 7, pp 2452-2461).
As c-Myc can be upregulated in acute myeloid leukemia, the oncogenic function of c-Myc has been studied and its exact role in myeloid leukemogenesis has been studied. Recently, some scientist found that Myc preferentially stimulated the growth of myeloid progenitor cells in methylcellulose and showed that Myc is a critical downstream effector of myeloid leukemogenesis (ibid.).
The finding that c-Myc plays a critical role in myeloid leukemogenesis indicates that by inhibiting an activation of c-Myc protein, an acute myeloid leukemia can be cured or prevented.
On the other hand, enzymes of the cytochrome P450 (CYP) superfamily are the major determinants of half-life and execute pharmacological effects of many therapeutic drugs. The human cytochrome P450 (CYP) 3A subfamily, includes CYP3A4, which is most abundant in the human liver (˜40%) and metabolizes more than 50% of clinically used drugs (Shimada et al 1994; Rendic and Di Carlo 1997).
Due to the key role of CYP3A4 in drug metabolism, significant inactivation of this enzyme could result in marked pharmacokinetic drug-drug interactions. Inhibition of CYP3A4 may cause severe drug toxicity through the enhanced exposure to coadministered drugs (Dresser et al 2000). For example, when irreversible CYP3A4 inhibitors such as erythromycin or clarithromycin are coadministered with terfenadine, astemizole, or pimozide patients may experience Torsades de pointes (a life-threatening ventricular arrhythmia associated with QT prolongation) (Spinler et al 1995; Dresser et al 2000). Cancer patients, at times, undergo multiple treatment regimes, which increases the risk of drug-drug interactions followed by adverse drug reactions.
Therefore, in developing therapeutic agents, especially when it is to be administered in combination with other drugs, there is a need for providing compounds having less CYP3A4 inhibitory activity.